Conventional sled test facilities operate with either one or two tracks and require rocket motors to move the sled down the track. Gravity profile is difficult to control and a water braking system is required to slow the sled down to a stop. The water has to be replenished and the water gates have to be replaced after every sled run, making it difficult to make more than one sled run per day. Tests can only be conducted in one direction on a conventional sled. After a run, the sled must be hauled back to the blockhouse area, where it is reinstrumented and new rocket motors are installed. There is always a danger that the sled may leave the track during any run. A conventional sled can only be operated during fair weather since the track and sled are both exposed to the elements.
The present invention utilizes a tube having the sled or carrier carried therein. Pressure differentials are created on opposite ends of the sled. This is done by opening the tube on one end of the sled and pressurizing the tube at the other end of the sled. Thus the present invention overcomes the disadvantages associated with a conventional sled test facility by eliminating the rocket motors and operating in a tube which may be placed underground, if desired. The use of a pressure differential system to establish the g-profile also eliminates the need for a water brake to stop the sled since reversing the pressure differential accomplishes the same purpose. Consequently, the present invention allows many sled runs to be made per day, since the sled can be run in either direction and does not require the installation of rocket motors after each test. The tubular track facilitates 24 hours, all weather operation since the track temperature will be nearly constant and the sled will not be exposed to changing weather conditions if the tube is underground.